Condensed Consolidated Statements of Changes in Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Accumulated Distributions in Excess of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Interest Rate Swap [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Preferred Stock [Member]	Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member] Common Stock [Member]	Additional Paid-in Capital [Member] Preferred Stock [Member]	Additional Paid-in Capital [Member]	Parent [Member] Interest Rate Swap [Member]	Parent [Member] Common Stock [Member]	Parent [Member] Preferred Stock [Member]	Parent [Member]	Noncontrolling Interest [Member]	Interest Rate Swap [Member]	Common Stock [Member]	Preferred Stock [Member]	Total
Balance at Dec. 31, 2011	$ (702,999)		$ (107,660)		$ 954		$ 4,069			$ 5,492,022				$ 4,686,386	$ 193,757				$ 4,880,143
Balance (in Shares) at Dec. 31, 2011					954		406,938
Contributions from noncontrolling interests															822				822
Comprehensive income:
Net income	53,638													53,638	5,510				59,148
Other comprehensive income:
Change in unrealized gain on marketable securities			1,159											1,159					1,159
Change in unrealized gain on interest rate swaps		193									193					193
Change in foreign currency translation adjustment			50,911											50,911	3,267				54,178
Redeemable noncontrolling interests															(1,582)				(1,582)
Dividends	(92,887)													(92,887)					(92,887)
Distributions to noncontrolling interests															(5,362)				(5,362)
Issuance of stock				16		11		18,055	387,214			18,066	387,230				18,066	387,230	18,066
Issuance of stock (in Shares)				16		1,093
Surrender of restricted stock																			(1,023)
Exercise of common stock options							3			4,767				4,770					4,770
Exercise of common stock options (in Shares)							320
Amortization of equity awards										4,815				4,815					4,815
Surrender of common stock										(1,023)				(1,023)					(1,023)
Surrender of common stock (in Shares)							(53)
Repurchase of common stock							(14)			(26,082)				(26,096)					(26,096)
Repurchase of common stock (in Shares)							(1,385)
Balance at Mar. 31, 2012	(742,248)		(55,397)		970		4,069			5,879,768				5,087,162	196,412				5,283,574
Balance (in Shares) at Mar. 31, 2012					970		406,913
Balance at Dec. 31, 2012	(824,008)		(66,182)		102		4,078			5,651,170				4,765,160	167,320				4,932,480
Balance (in Shares) at Dec. 31, 2012					102		407,782
Contributions from noncontrolling interests															49				49
Comprehensive income:
Net income	67,770													67,770	2,738				70,508
Other comprehensive income:
Change in unrealized gain on marketable securities			6,767											6,767					6,767
Change in foreign currency translation adjustment			31,737											31,737	1,273				33,010
Redeemable noncontrolling interests															(1,415)				(1,415)
Dividends	(100,382)													(100,382)					(100,382)
Distributions to noncontrolling interests															(1,912)				(1,912)
Issuance of stock						5		9,078				9,083					9,083		9,083
Issuance of stock (in Shares)						555
Surrender of restricted stock							(1)			(1,948)				(1,949)					(1,949)
Surrender of restricted stock (in Shares)							(90)
Exercise of common stock options							4			5,768				5,772					5,772
Exercise of common stock options (in Shares)							376
Amortization of equity awards										3,777				3,777					3,777
Balance at Mar. 31, 2013	$ (856,620)		$ (27,678)		$ 102		$ 4,086			$ 5,667,845				$ 4,787,735	$ 168,053				$ 4,955,788
Balance (in Shares) at Mar. 31, 2013					102		408,623